A report discusses Ka-band (35-GHz) radar for mapping the surface topography of glaciers and ice sheets at high spatial resolution and high vertical accuracy, independent of cloud cover, with a swath-width of 70 km. The system is a single-pass, single-platform interferometric synthetic aperture radar (InSAR) with an 8-mm wavelength, which minimizes snow penetration while remaining relatively impervious to atmospheric attenuation.
As exhibited by the lower frequency SRTM (Shuttle Radar Topography Mission) AirSAR and GeoSAR systems, an InSAR measures topography using two antennas separated by a baseline in the cross-track direction, to view the same region on the ground. The interferometric combination of data received allows the system to resolve the path length difference from the illuminated area to the antennas to a fraction of a wavelength. From the interferometric phase, the height of the target area can be estimated. This means an InSAR system is capable of providing not only the position of each image point in along track and slant range as with a traditional SAR but also the height of that point through interferometry.
Although the evolution of InSAR to a millimeter-wave center frequency maximizes the interferometric accuracy from a given baseline length, the high frequency also creates a fundamental problem of swath coverage versus signal-to-noise ratio. While the length of SAR antennas is typically fixed by mass and stowage or deployment constraints, the width is constrained by the desired illuminated swath width. As the across-track beam width which sets the swath size is proportional to the wavelength, a fixed swath size equates to a smaller antenna as the frequency is increased. This loss of antenna size reduces the two-way antenna gain to the second power, drastically reducing the signal- to-noise ratio of the SAR system. This fundamental constraint of high-frequency SAR systems is addressed by applying digital beam-forming (DBF) techniques to synthesize multiple simultaneous receive beams in elevation while maintaining a broad transmit illumination. Through this technique, a high antenna gain on receive is preserved, thereby reducing the required transmit power and thus enabling high-frequency SARs and high-precision InSAR from a single spacecraft.
The Ka-band digital beam-forming interferometric mapper will provide critical data on the mass changes of the Earth's ice cover and contribute data to improved estimates of ice sheet contribution to sea-level rise, as outlined in the Climate Variability and Change road map. The comprehensive measurements will come from the swath, temporal sampling capability, variable resolution, and accuracies unique to this system.
This work was done by Delwyn K. Moller, Gregory A. Sadowy, Eric J. Rignot, and Soren N. Madsen of Caltech for NASA's Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Physical Sciences category. NPO-43962
This Brief includes a Technical Support Package (TSP).
Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets
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Overview
The document outlines a NASA Technical Support Package for a cutting-edge innovation titled "A Ka-Band Digitally Beamformed Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets," identified by NTR Number 43962. Developed by NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, this technology represents a significant advancement in the field of remote sensing and geospatial analysis.
The primary purpose of this radar interferometer is to facilitate high-resolution topographic mapping of glaciers and ice sheets, which are critical components of the Earth's climate system. Understanding the dynamics of these ice formations is essential for predicting sea-level rise and assessing the impacts of climate change. The Ka-band frequency utilized by this radar system allows for enhanced precision in measuring surface elevations and changes over time, providing valuable data for scientists and researchers.
The document emphasizes that the information contained within is part of NASA's Commercial Technology Program, which aims to disseminate aerospace-related developments that have broader technological, scientific, or commercial applications. This initiative underscores NASA's commitment to innovation and collaboration with various sectors to leverage advancements in technology for societal benefits.
Additionally, the Technical Support Package includes contact information for further inquiries, specifically directing interested parties to the Innovative Technology Assets Management at JPL. This resource is intended to facilitate partnerships and collaborations that can enhance the application of the technology described.
It is important to note that the document contains proprietary information and is subject to U.S. export control regulations. As such, users are advised to comply with all applicable laws when utilizing the information provided.
In summary, the document serves as a comprehensive overview of a significant technological advancement in radar interferometry, aimed at improving our understanding of glaciers and ice sheets. By making this information available, NASA seeks to foster innovation and collaboration that can lead to impactful scientific discoveries and applications in the context of climate change and environmental monitoring.
